Conventionally, a vehicle air conditioner is known to be capable of switching between air-heating of a vehicle interior using a high-pressure refrigerant in a vapor compression refrigeration cycle and air-heating of the vehicle interior using a heat source other than the refrigeration cycle (for example, exhaust heat from an internal combustion engine) (see, for example, Patent Document 1).
The vehicle air conditioner described in Patent Document 1 is designed to switch between the air-heating of the vehicle interior using a coolant in the internal combustion engine when the coolant is at a high temperature and the air-heating of the vehicle interior using the high-pressure refrigerant in the refrigeration cycle when the coolant is at a low temperature. In the technique described in Patent Document 1, a heater core that dissipates heat from the coolant into ventilation air to be blown into the vehicle interior is disposed on an upstream side of an air flow with respect to a condenser that dissipates heat from the high-pressure refrigerant into the ventilation air.    Patent Document 1: Japanese Unexamined Patent Application Publication No. 05-221233